Current sensors are used for a variety of applications, for example current limitation, over-current protection or simply for monitoring the intensity of a current. For such applications, Hall-sensors or similar sensors are widely used. Hall-sensors sense the magnetic field of the current and provide a voltage (Hall voltage) proportional to the intensity of the current. As the magnetic field decreases with increasing distance between the magnetic field sensor and the current, the semiconductor die comprising the Hall-sensor has to be brought close to the conductor carrying the current to be measured to have a sufficiently strong magnetic field.
U.S. Patent Publication No. 2008/0297138 A1 describes a current sensor with lead frames forming a current conductor portion and a substrate comprising a magnetic field sensing element arranged above a current conductor portion provided by the lead frame to measure the current flowing through the current conductor portion. Also U.S. Pat. Nos. 7,166,807 B2 and 6,995,315 B2 describe current sensors with magnetic field sensors based on the lead frame technology as structural-design technology.
U.S. Pat. No. 5,041,780 describes an integrable current sensor, wherein a current conductor is provided on top of a semiconductor substrate comprising the magnetic field sensing elements. A further example of a semiconductor device with a Hall-effect element and a conductor arranged on top of the semiconductor substrate is described in U.S. Pat. No. 6,424,018 B1.
Current sensors based on lead frame structures or semiconductor carriers or ceramic carriers cause high costs with regard to the material and with regard to the production processing. Furthermore, the current to be measured produces eddy currents in neighboring conductors or conductive layers, for example used as electrostatic shields, wherein the eddy currents in return produce magnetic fields that superimpose to the magnetic field of the current to be measured, and thus deteriorate the sensitivity and the calibration of the current measurement of the sensor.
German Patent publication DE 10 2006 026 148 A1 describes an electronic device comprising a load current path consisting of two conductor traces arranged on top of each other in a multi-layer printed circuit board and insulated by the printed circuit board from each other. The device further comprises a Hall-sensor arranged below the printed circuit board and the two conductor traces for a current measurement of the load current path. The Hall-sensor is electrically connected to a measurement evaluation unit via conductor traces on the lower surface of the printed circuit board. Current sensor arrangements as described in German Patent publication DE 10 2006 026 148 A1 are expensive to produce, expensive to test, only show a limited measurement sensitivity, which additionally deteriorates over the lifetime of the electronic device.